This invention relates to superconducting magnets and, more particularly, to a superconducting magnet assembly suitable for use as a magnetohydrodynamic generator having an improved superstructure for supporting and enclosing the magnet substructure thereof.
Magnetohydrodynamics (MHD) is a method of generating power by directly converting fuel energy into electrical energy. In a MHD generator, fuel is combusted so as to produce a very high temperature, high pressure ionized gas commonly termed plasma. The plasma generated in the MHD burner is passed through a channel immersed in a high strength magnetic field generated by a plurality of superconducting magnets flanking the channel. The plasma passing therethrough induces an electrical current which is gathered on electrodes lining the channel.
Because of the high efficiency associated with the direct conversion mechanism of magnetohydrodynamics, major development efforts are underway to produce commercial scale MHD generators. One problem encountered in designing the commercial MHD generator is providing a superstructure for supporting and enclosing the superconducting magnets which is capable of withstanding the high stresses created when the superconducting magnets are energized.
The superconducting magnet assembly of a MHD generator typically comprises a substructure of a plurality of elongated symmetrical magnet pairs flanking the channel through which the plasma passes. One magnet of each symmetrical pair is disposed on one side of the channel and its corresponding counterpart is disposed on the other side of the channel. When energized, the magnet pairs want to deform into a circular shape. That is, the individual magnets repel each other in inverse proportion to the square of the distance between conductors in which current directions are opposite. Likewise, there is an attraction between conductors in which current directions are the same thereby causing the individual magnets to be attracted in inverse proportion to the square of the distance between conductors. Thus, a magnet unrestrained will deform into a circle so as to equalize the repulsive and the attractive forces so generated.
Additionally, the superconducting magnet assembly must be continuously cooled to near cryogenic temperatures, i.e., near absolute zero, in order for the magnets thereof to maintain their superconductivity. As a result, the superstructure for encircling and supporting the superconducting magnet substructure must not only effectively absorb and equilibrate the stresses generated when the magnets are energized, but must also be designed to utilize a minimum of material mass and to occupy a minimum of volume so as to minimize cooling requirements.